Abstract

A pronounced hump structure at about −5 V in the high-frequency capacitance-voltage curve of an undoped InGaN/GaN heterostructure is observed and this hump weakens gradually with decreasing measurement frequency, indicating the occurrence of an inversion behavior in the InGaN/GaN heterostructure. The inversion behavior in the curve is attributed to hole accumulation at the heterointerface where a hole well is formed due to the strong piezoelectricpolarization effect in the InGaN/GaN heterostructure. The acceptor traps related to Ga vacancies in the InGaN layer are thought to be the source of the minority carriers. The theoretical calculation of band diagram of the InGaN/GaN heterostructure confirms the formation of the hole well at the heterointerface and supports the behavior of hole accumulation under negative bias voltage.

Received 13 April 2009Accepted 22 June 2009Published online 10 July 2009

Acknowledgments:

This work was supported by the Natural Science Foundation of Jiangsu Province (Contract Nos. BK2006126 and BK2008019), National 863 project (Contract No. 2007AA06A405), the National Natural Science Foundation of China (Grant Nos. 60721063 and 60825401), and Special Funds for Major State Basic Research Project 973 (Contract No. 2009CB320300).